What’s All the Hype? Feeding the Energetic Horse

Some simple diet changes might help calm your hyperactive horse

He’s impossible to catch in the pasture when out with his herdmates. He’s jigging about while you tack him up. And he eyes every blade of grass beside the arena suspiciously, as if one might reach out and grab a fetlock at any moment.

Some might say he’s “feeling his oats,” pointing at nutrition as the cause of his hyperactivity. Could a simple grain change bring this four-legged kite back down to earth? Let’s find out.

Pinpointing the Cause

Many factors can influence a horse’s hyperactivity, including genetic predisposition, experience and learning, management, and nutrition. In most cases multiple factors play a role in this behavior and, without a complete understanding of each, it’s easy to single out nutrition, specifically concentrates, as the main culprit.

In the Feed Bucket

Whether or not that half-scoop of concentrate twice a day is attributing to extreme hyperactivity depends on calories—units of energy—in the overall diet.

A horse’s daily energy requirement depends on his physiological stage and activity level. The 2007 Nutrient Requirements for Horses sets guidelines for maintenance, growth, reproduction, and exercise. In most cases, excess energy results in weight gain, but it can also manifest outwardly as hyperactive behavior. Carbohydrates and fats make up the two main calorie sources in a horse’s diet. Forage, both as hay and pasture, and concentrates contribute to the carbohydrate portion, while oil and oilseeds, such as flaxseed and rice bran, contribute to fats. Contrary to popular belief, protein is not a primary energy source for horses and does not contribute to hyperactivity.

How the body breaks down and stores energy depends on the composition of the diet. Structural carbohydrates, better known as fiber, pass through the small intestine undigested and undergo microbial fermentation in the hindgut (the intestinal tract beyond the small intestine) to form the volatile fatty acids (VFAs) acetate, butyrate, and propionate. The horse’s body can use some VFAs, like acetate, directly for energy while other VFAs must undergo changes before they can be used for energy.

Nonstructural carbohydrates (NSCs, another energy source), or hydrolysable carbohydrates, on the other hand, are found in cereal grains and pasture. These include sugars, starches, and fructans, a type of sugar found in grasses. Specific enzymes break down NSCs in the small intestine into glucose, which passes through the intestinal wall and into the bloodstream. This causes blood glucose to rise until insulin signals cells to take up glucose for storage, returning blood levels to normal. High-sugar and starch meals keep glucose levels elevated longer after the horse has finished eating, until insulin can bring them back to normal. Structural carbs do not have the same effect on blood glucose and insulin as NSCs do.

Elevated glucose levels in the bloodstream might contribute to hyperactive behavior by initiating the horse’s “fight or flight” response. Under stressful circumstances, the hormone cortisol increases blood glucose levels, giving the horse a burst of energy to flee from potential danger. This rise in blood glucose is similar to that experienced after a meal containing high amounts of NSCs. By replacing some calories from NSCs with fiber and fat, owners might be able to reduce hyperactivity.

While pursuing her master’s degree at Virginia Tech, Janice Holland, PhD, PAS, associate professor of Equine Studies at Midway University, in Kentucky, evaluated the effects of fat supplementation on young horse behavior by measuring distance traveled and startle response. After adding 10% fat to a grain meal, both parameters appeared to decrease, she said. Building on that, Holland and colleagues replaced some of the starch and sugar with fat and fiber in the grain meals of 4- to 5-month-olds and, during the weaning process, recorded locomotion and vocalizations to assess stress.

“Weanlings on the fat and fiber diet spent less time walking and trotting, had fewer vocalizations, and traveled less distance,” she says.

Subjectively, in a 2000 study out of the University of Minnesota, researchers found Thoroughbreds consuming high-fat diets to be calmer and easier to work with than those consuming high-starch diets.

In Their Genes

Behavior and personality are heritable and can differ among breeds. This is seen particularly in dogs, where distinct differences exist between breeds in traits such as aggression and sociability. Researchers in Germany tested temperament in response to basic handling in two generations of Angus and Simmental calves and found the Angus calves to be consistently easier to handle. And researchers see these differences among horses, too. In 2007 Lloyd et al. used a trait-based assessment to categorize personality types in more than 1,200 horses of eight breeds using “The Horse Personality Questionnaire” (see Table 1 below).

The team found that the Arabian breed scored highest in anxiousness and/or excitability. Welsh ponies, cobs, and the Thoroughbred—breeds with direct ties to the Arabian—also scored high in these traits. Therefore, hyperactivity appears to be somewhat related to breed and might explain these horses’ predisposition to excitability even in familiar locations.

Management

Feeding practices tend to have a greater effect than do housing and management, but the latter can cause equine behavior problems. They are rarely related to a single factor, and many can be tied to confinement. In 1991, Krzak and colleagues found that when confined with no daily exercise, yearlings exhibited more wood-chewing behavior than those exercised once a day.

“Under free-ranging circumstances, horses will wander and spend 60% of their day foraging,” says Karen Overall, MA, VMD, PhD, Dipl. ACVB, senior research scientist at the University of Pennsylvania’s New Bolton Center, in Kennett Square. “The remainder of their time is spent standing, lying down, or engaging in another activity.”

Free-range movement is also part of horses’ play development. “The social experience of play is important for normal social interaction in adult life,” she says.

Bad Habits

A horse’s innate flight response can motivate him to get away from a stimulus, rejoin the herd, or return to the barn. Horses expressing this type of hyperactivity shy, jog in place (jig), or bolt frequently. Shying, for example, is an avoidance response that sends horses leaping laterally or backward away from a sound, object, or smell. Many horses in unfamiliar surroundings exhibit this behavior, but some might also shy at objects in familiar locations. Why is that?

The hyperactive horse learns to ignore pressure when he wants to remove himself from a perceived threat or return to a group. These horses might jig or jog and are unresponsive to repeated walk signals, often extending the neck to pull the reins through the rider’s hands. Similarly, these horses can bolt or gallop off with no response to repeated rein pressure to stop.

Taming the Beast

Implementing some simple diet and management changes might take the edge off your nervous nelly, but know that you might not see results overnight … or at all. Body condition scoring (BCS) is the best way to determine if the horse’s diet meets or exceeds his daily calorie needs. This system rates fat cover at the ribs, shoulder, withers, neck, loin, and tailhead on a scale from one (extremely emaciated) to nine (extremely fat).

With easy keepers, a simple change in concentrate could help alleviate some hyperactivity. Ration balancers contain lower levels of sugar, starch, and calories and provide a concentrated source of amino acids, vitamins, and minerals if the forage is deficient in these nutrients. Most mature horses can meet their necessary daily nutrient requirements by consuming one to two pounds of a ration balancer pellet per day.

For those needing more calories from concentrate to maintain weight or for performance, consider either a high-fat grain mix or top-dressing fat. Adding fat as a calorie source might reduce some hyperactive behavior, as seen with Holland’s research.

It’s easy to point fingers at the concentrate portion of the diet, but most commercial grain mixes—even those with added molasses—contribute very little sugar to the diet. Pasture grass, on the other hand, can be composed of up to 50% carbohydrate from sugars, potentially supplying the same amount of calories as a racing-type feed, pound for pound. Limiting pasture access to 12 hours per day and supplying free-choice grass hay in the stall can help control NSC intake. And using a grazing muzzle during turnout can help reduce carbohydrate consumption, especially when pasture is particularly lush.

Fiber provides the horse with more than just calories. Study results have shown that when horses consume less than 1% of their body weight per day in fiber, they are more prone to develop unwanted behavioral vices such as stall-walking. Fiber, particularly in the form of long-stemmed hay, slows the horse’s rate of dietary intake and reduces boredom. When out on pasture, horses generally consume grass constantly, so it’s important to mimic this as closely as possible for stalled horses. Research from the University of Minnesota shows that horses take 3.4 hours to consume a hay meal from the stall floor, compared to 6.5 hours from a slow-feed haynet.

Considering a calming supplement? The sheer number of choices can be overwhelming. Most oral calming supplements provide minerals, vitamins, amino acids, and/or herbs in various amounts claimed to calm the hyper or nervous horse. Table 2 provides a list of the more common ingredients found in commercially available calming supplements.

Little or no supportive evidence exists proving most of these ingredients reduce nervousness or anxiety. However, Jessica Dodd and a team at Charles Sturt University, in New South Wales, Australia, in collaboration with WALTHAM, recently conducted the first scientific pilot study to investigate magnesium’s effects on behavior. They looked at the effects of an additional 10 grams of magnesium (as magnesium aspartate) on flight speed after horses were startled, under safe controlled conditions, and saw a significant reduction in flight speed response with the additional magnesium.

Take care when administering calming supplements to competition or racing horses, as many equestrian organizations have banned certain ingredients. For example, the United States Equestrian Federation (USEF) in its Guidelines for Drugs and Medication defines a forbidden substance as a product or drug containing an ingredient that might affect the performance of a horse and/or pony as a stimulant, depressant, tranquilizer, analgesic, local anesthetic, or psychotropic (mood- and/or behavior-altering) substance. In fact, the USEF goes on to strongly caution against using herbal or natural products, especially those the manufacturers claim as permitted or undetectable by drug tests. Chamomile, devil’s claw, lavender, and valerian are all on the USEF’s list of forbidden substances.

Take-Home Message

Multiple factors can cause a horse to be hyperactive. Be mindful of breed, management, and nutrition when trying to pinpoint probable causes for this behavior. Dietary changes and management techniques aimed at lowering sugar and starch intake can help alleviate feed-related idiosyncrasies.